JPS5964805A - Auto-focusing device - Google Patents

Abstract

PURPOSE:To improve the operation precision by inserting a gate circuit which eliminates an unstable signal part of an impulsive signal waveform. CONSTITUTION:The pulse light emission timing signal of a light source from a timing generating circuit 57 is inputted to a pulse shaping circuit 241 of a gate circuit 24, and a prescribed waveform is outputted from the pulse shaping circuit 241 on a basis of this timing signal and is inputted to the base of a transistor TR as a switching element, and then, the TR is turned off only during a prescribed timing, and a distance signal VX is inputted to a storage means 51. Thus, the signal waveform based on delay and noise is not stored in the storage means, and the normal distance signal is stored, thereby improving the operation precision.

Description

Detailed Description of the Invention The present invention is an automatic focusing device that optically detects the distance to an object and moves the lens of a camera or the like based on the signal to focus the object image on a recording material. In detail, we have improved the configuration of the calculation circuit that outputs a signal corresponding to the distance to the object from the signal from the optical detection element that detects the reflected light from the object, improving calculation accuracy. It is something.

Now, conventional p 3 [) (p 03itiOn S
It is known to measure the distance to an object using a semiconductor device detector that outputs a pair of current signals related to the position of a light spot formed on a light-receiving surface, such as ens+t+veDevice), and outputs a distance signal. ing. For example, a PSD has a band-shaped light receiving surface as shown in Fig. 1. For example, if the length of the light receiving surface is L and a light spot is formed at a point x apart from the center, then Currents Il and I2 shown by the following equations flow in the direction.

Is = (L/2-x) ・I/L--(1)I2
= (L/2+'x') ・r/L--<2) However,
I: Charge current generated in the optical switch ((1), (2) above)
From the formula, (12-Il)/(Is + I2) is found, (Iz It)'/ (II + I2) = 2x
/L ......(3>), which is proportional to Using the distance signal output from the arithmetic processing circuit, 1L of cameras, video cameras, etc.
It was shown in Japanese Unexamined Patent Publication No. 57-22508 that it can perform the function of automatic focus adjustment of imaging equipment, and the patent application No. 56-1989 was published.
No. 178583 and other applications have been filed to improve the performance of distance measuring devices. That is, the distance device irradiates light emitted from a light source toward a distance target point via a light-emitting lens, and forms a light spot by the reflected light on the light-receiving surface of a semiconductor device detector using a light-receiving lens. , the pair of current signals 1 and 2 output by the semiconductor device detector is given to an arithmetic processing circuit, and the arithmetic processing circuit calculates VX = k In (It /I2), where r+ ,
Iz: A current value obtained by removing the rough ground light component from the pair of output signals of the semiconductor device detector: Vx, which is expressed as a constant, is determined, and this is an example of an arithmetic circuit configuration in which this is output as a distance signal. This is Figure 2. 1 is a semiconductor device detection device (PSD), 2 and 2' are PSD
A pair of current signals 1+ from l.

3 and 3'
is the above 1x, r? Of the voltage signal corresponding to the DC component (
It is an AC amplifier that cuts off the reflected light component (generally reflected light from the background), and then passes through a logarithmic amplifier 20 and 21, and then inputs the difference to a differential amplifier 22 that outputs
A distance signal QVX corresponding to l(It/I2) can be output.

In the figure, Vn+, vn2. Vns+Vn4 is input to the non-inverting input terminal of the amplifier group, and is used to adjust the characteristics of the PSD, the offset voltage of the preceding stage amplifier, etc. 23 plays the role of bias adjustment of the differential amplifier 22, and the default detection circuit 30 is for detecting whether the accuracy of distance measurement calculation can be guaranteed. Since the distance is determined by , the calculation accuracy cannot be guaranteed if the value of 11°3-12 becomes small.

Therefore, when the current 11.12 drops below a certain level, the default detection circuit 30 sends a signal indicating that distance measurement is not possible.
Output to . Distance measurement is generally not possible when measuring long distances, and in this case, the light spot is located at the PS shown in Figure 1.
It moves to the right of the D light receiving surface and becomes II < 12.

Therefore, it is preferable to apply the output voltage of the AC amplifier 3 on the current II side to the default detection circuit 30.

Now, when the distance signal is output in this way, the distance signal ■× is generally stored in the storage means 4 as an automatic focus adjustment device.
When the lens position is moved to bring it into focus, a signal corresponding to the lens position changes, and when it matches the distance signal VXI11 in the storage means, the lens movement is stopped.

Conventionally, the light emitted from a light source for distance measurement is pulsed and is only turned on for a relatively short predetermined period of time, and a distance measurement signal is also output for a correspondingly short period of time. Therefore, the input characteristics of the storage means must have a high-speed response, and the signal must be stored while the camera is operating.
Has a peak hold function.

However, the distance signal v× from the arithmetic circuit is It, I
If the delay times of the two series are constant, Vx should be constant within the pulse time, but if the delay times are different, the rise and fall portions of VX will become unstable, and for example, the inverting input terminal of a differential amplifier When a delay occurs in the side input signal, that is, the I2 component, VX rises in the latter part, and in the storage means that holds the peak, it is likely to be stored at a higher voltage than the normal distance measurement signal. In addition, since the irradiation light is pulsed and has a very small amount of light, the current output from the PSD is also small.
In particular, the transient state of the Vx signal rising and falling tends to become unstable. First, Figure 3 (I) shows the ideal
In other words, in the case where there is no delay or noise, the signal waveform at each point of the arithmetic circuit that obtains the distance lll11 signal from the output of the conventional PSD is as follows: (b) is the output of .3', and (C) is the output of logarithmic amplifier 20.21.

(d> is the output of the differential amplifier 22, that is, the distance signal Vx, which is preset by the bias adjustment circuit 23 when the distance measurement target point is at a preset reference distance (distance where It=rz). This specific circuit establishes a linear relationship between the output voltage v x which is the reciprocal of the distance to the object to be measured (between 11 and 12 on the horizontal axis (corresponds to the pulsed light emitting state of the light source).(A) in Figure 3 shows the voltage signal waveform on the f1 current side.
(b) does not show the waveform on the ■2 current side. Further, the waveform shown in (e) is the signal waveform at each timing when the distance signal vx is stored in the storage means 4.

However, in this circuit configuration, r! Current side signal and 12
The current side signal tends to be delayed with respect to the optical input pulse width t1 to t2 to the PSD, and if the delay times of both series are different, 12 series (differential If the inverting input side of the amplifier 22 is delayed, a rise occurs near t? of <Vx as shown in (d) of FIG. 3 (I[>), and the storage means stores a voltage with a large error ( This state is shown as VXII+ in (e) of Figure 3 (If))
. A similar phenomenon may occur in the case of transient instability. Furthermore, when random noise occurs in the distance signal vx itself, the storage means may store the peak of the noise.

In this way, the conventional arithmetic circuit outputs the distance measurement signal, and
Controls the movement of optical systems such as lenses based on this distance signal as an automatic focus adjustment device! I],
If an abnormally high level is stored due to noise or non-uniformity of circuit characteristics, the lens will move in a completely different manner, resulting in an out-of-focus image.

The present inventor has devised a method to delete unstable signal portions near the front and rear ends of the pulsed signal waveform in the signal path from the conventional distance signal output terminal (output of a differential amplifier) to the storage means. By inserting such a gate circuit, the above problem has been overcome.

That is, a semiconductor device detector that receives pulsed reflected light from an image and outputs a pair of current signals that vary depending on the light receiving position, and a signal that is amplified appropriately based on a voltage signal based on the pair of current signals. 7- A differential amplifier for amplifying, a gate circuit for validating only the central part of the pulsed output of the differential amplifier, a storage means for storing the output of the gate circuit, and a signal stored in the storage means. The present invention can be achieved by an automatic focusing device that automatically adjusts the optical system and focuses automatically.

As mentioned above, when the arithmetic processing circuit (Fig. 2) that calculates the distance signal Vx is actually used, noise may be added to the distance doubler itself, or the circuit that calculates each of the pair of current signals output from the PSD. In the system, the distance signal v is determined by the difference in delay characteristics etc.
There is a risk that an abnormal waveform as shown in (d) of Fig. 3 ([) may appear in x. Therefore, (e) in Figure 3 (Ir)
) should be stored as shown by the broken line, but the distance signal vxIl that is stored looks like the actual distance signal, which is inconvenient.

Therefore, as shown in FIG. 4(I), a gate circuit 24 is inserted before the storage means 4. This gate circuit 24 receives a gate timing signal from a timing generation circuit 57 that provides the light emission timing of the light source for distance measurement of the device and the memory timing of the storage means 51, and generates a distance signal VX based on the gate timing signal. Only approximately the center portion (js to t4 timing) is passed to the storage means 51, and the front and rear ends of the pulse-like signal waveform are cut off. Here, the pulse multiplication timing waveform (A) of the timing generation circuit 57h'X and others to the light source and the gate timing waveform (B) of the gate circuit 24 are shown in FIG. 4 (II).

As an example, for example, a light emission timing pulse width of 1'5
In the case of 0μsec, divide it into three equal parts and take 50μsec in the center.
Although very good results were obtained by using c as the gate timing pulse (t3 to j+), the present invention is not limited to this embodiment. A gate is applied so that only signals near the center are input into the storage means as correct signals. As a specific example of how to apply a gate, a transistor is shown in FIG. 5 of Tonki.

FIG. 3 (I [[) is provided with a gate circuit, and FIG. The relationship with timing (t, between a and 14) is shown. Now, in conventional automatic focusing, either active or puzzling, a pair of current waveforms are generated by the PSD and calculations are not performed for each of them. Although this was not necessary, it will become a serious problem if automatic focusing devices using PSD are used frequently in the future, and the present invention will be utilized as an effective countermeasure for this problem.

FIG. 5 is a configuration diagram showing the main parts applied to a camera as an embodiment of the automatic focus adjustment device of the present invention. Note that the same parts as in each of the above figures are given the same reference numerals, and the explanation thereof will be omitted. In the figure, 50 is the above-mentioned arithmetic processing circuit (shown in FIG. 4), 51 is a storage means (corresponding to "4" in FIG. 4) for temporarily storing the output signal Vx of the arithmetic processing circuit 50, and 52 is a distance measuring circuit. 53 is a position detector such as a potentiometer that detects the amount of extension of the shadow lens 54. Further, 55 is a lens start circuit that stops energizing the solenoid SQL+ and starts moving the projection lens 54 by a spring SP, and 56 is an output VX of the storage means 51.
When II11 and the output vl of the lens position detector 53 match, the solenoid SQ L 2 is a lens control circuit that stops energizing and stops the movement of the photographing lens 54. 5
Reference numeral 7 denotes a timing generation circuit, which is used to execute an autofocus operation in a predetermined sequence, and generates a pulse emission timing to the light source and a signal to create a gate timing to the gate circuit 24.

The gate circuit 24 (within the broken line) in FIG. 5 first sends the pulse emission timing signal ((A) in FIG. 4 (II)) of the light source from the timing generation circuit 57 to the pulse shaping circuit 241 in the gate circuit 24, for example. input, pulse shaping circuit 24
1, based on that, the waveform of (B) in Figure 4(n) is outputted and inputted to the base 11- of the transistor which is a switching element, so that the transistor is at 0FFL and the distance signal is output only during the timing from 13 to t4. Vx is input to storage means 51. In addition, 58 is a shutter, 59
indicates film.

First, when the release switch S1 is turned on, the timing generation circuit 57 sends a pulse signal to the light emitting circuit 52 after a predetermined period of time has elapsed, causes the LEDlo to emit light for a certain period of time, and causes the arithmetic processing circuit 50 to calculate the distance signal Vx. This is the output V xm of the storage means 51.

Continuously output as . Furthermore, the timing generation circuit 57 sends a control signal to the lens start circuit 55,
Cut off the power to solenoid 5OL1.

As a result, the photographing lens 54 moves, and the output V1 of the lens position detector 53 decreases. Then, at the same time that VXJ=Vt, the lens control circuit 56 de-energizes the solenoid S OL 2, and the photographing lens 54 stops at the in-focus position.

Of course, it goes without saying that the present invention can be achieved by using other means and methods as shown in FIG. 5 regarding the movement mechanism and control of the camera lens.

-12= As described above, the present invention can eliminate delays and noises that occur in a pair of current signals output from a semiconductor device detector that can be applied to an autofocus camera and their respective calculations. The above signal waveforms based on noise are not stored in the storage means, and a normal distance signal can be stored, thereby achieving an effective automatic focusing device.

[Brief explanation of drawings]

FIG. 1 shows the light receiving surface of a semiconductor device detector (PSD) and a state where the light receiving spot is shifted by X from the reference position. Second
The figure shows an example of a conventional circuit configuration in which a PSD is used to calculate a pair of current signals output from the PSD, output a distance signal vx, and input it to a storage means. , Figure 3 (I) (n) ([
1) shows signal waveforms of various parts in the arithmetic processing circuit and storage means. FIG. 4(I) outputs a distance signal according to the present invention,
An example of the configuration of an arithmetic circuit input to the storage means is shown. FIG. 4(n) shows an example of the relationship between the pulse emission timing of the light source and the gate timing. FIG. 5 shows an example of the configuration of an automatic focus adjustment device including the essential parts of the present invention. 1...Semiconductor device detector (PSD) 2.2'...Current voltage converter (IV converter) 3.3
'... AC amplifier 20.21... Logarithmic amplifier 22... Differential amplifier 4.51... Storage means 56... Lens control circuit Vx... Distance signal output V xm, V X1lh...・Distance signal output from storage means Patent applicant Roku Konishi Photo Industry Co., Ltd. Agent Yoshimi Kuwahara M1 Figure 1 Display of events 1981 Patent application No. 175968-2 Title of invention Automatic focus adjustment device 3 Correction Relationship with the Raku Incident Patent Applicant Address 1-26-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Name (+27) Konishi Roku Photo T Gyo Co., Ltd. Representative Director Nobuhiko Kawamoto 4 Agent Address 191 Address Tokyo 1-5 Sakura-cho, Hino City Date of amendment order 6, “Detailed description of the invention” column of the specification subject to amendment, Figure 1 of the drawings 7, Contents of amendment (1) “Invention” of the specification "Detailed explanation of" is amended as follows. (2) Correction of drawings As shown in the attached sheet, 11 in Fig. 1 is replaced by 13, and ■ is replaced by engineering. 2-

Claims (1)

[Claims] a semiconductor device detector that receives pulsed reflected light from an image and outputs a pair of current signals that vary depending on the light receiving position, and amplifies the difference between a signal obtained by suitably amplifying a voltage signal based on the pair of current signals, respectively; A differential amplifier, a gate circuit that enables only the central part of the pulsed output of the differential amplifier, a storage means for storing the output of the gate circuit, and an optical system adjusted based on the signal stored in the storage means. An automatic focus adjustment device that automatically adjusts the focus.